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Repost Science Sphere In a groundbreaking proof-of-concept study, scientists have used CRISPR-Cas9 gene editing to remove the extra copy of chromosome 21 from cells with Down syndrome, effectively correcting the genetic imbalance at the cellular level. This condition, known as trisomy 21, affects approximately 1 in every 700 births and currently has no curative treatment.Led by Ryotaro Hashizume and colleagues, the team applied CRISPR to both pluripotent stem cells and skin fibroblasts derived from individuals with Down syndrome. The method not only eliminated the extra chromosome but also ensured the remaining pair originated from different parents—restoring normal gene function in the edited cells.By temporarily suppressing the cells' DNA repair mechanisms, the researchers boosted the precision and efficiency of chromosome removal. While this powerful technique is not yet ready for human application—due to potential risks of affecting the remaining chromosomes—it marks a pivotal step toward future therapies.If adapted safely for neurons and glial cells, this approach could eventually help reverse some cognitive and developmental effects of Down syndrome. Though clinical use remains distant, the research opens up bold new possibilities in chromosome-level gene therapy.Follow Science Sphere for regular scientific updates RESEARCH PAPER 📄Ryotaro Hashizume et al, "Trisomic rescue via allele-specific multiple chromosome cleavage using CRISPR-Cas9 in trisomy 21 cells", PNAS Nexus (2025)